Rheostat



J. BECKER lJuly l, 1930.

RHEOSTAT Filed Oct. 29, 1928 3 Sheets-Sheet l July l, 1.930. J, BECKER 14,769,732

Filed Oct. 29, 1928 3 Sheets-Sheet 3 Patented July l, 1930 UNITED STATES PATENT OFFICE JULIUS BECKER, OF CHICAGO, ILLINOIS, ASSIGNOR TO VACUUM CAN COMPANY, A CORPORATION 0F ILLINOIS RHEOSTAT Application led October 29, 1928.

The present invention relates to devices through which electric currents pass to their point of use and which are adapted to vary the characteristics of the current. The object of the present invention is to produce a device ofthis kind which will give a wide range of variations through a series of extremely small steps; in other words, to produce a device that will permit the current characteristics to be accurately regulated so as best to meet the requirements at any particular time.

In electro-plating, for example, it is common and necessary to employ a rheostat to control the strength of the current, but with the ordinary rheostat it is impossible to secure a nicety of regulation.

In the common type of knife switch rheostats, the resistance is diminished by closing o one switch after another, or increased by opening one switch after another, but leaving some resistance continuously in the circuit, making it often impossible to regulate the potential and current density to the desired value, while the adjusting is more or less a drawn out experiment requiring often so much time that before the predetermined value is obtained, the articles to be plated have received too much or too little current and potential, resulting in faulty plate.

These characteristics are much more distinct in the electro-deposition of chromium Where high current densities are employed and where an instantaneous regulation to a predetermined value is of necessity for success. Viewed in one of its aspects the present invention may be said to have for its object to produce a rheostat that will permit the resistance to be varied either 40 through large steps or through very small which require high current densities and a predetermined current value.

Viewed in another of its aspects the present invention may be said to have for its object to produce a rheostat that will permit the resistance to be adjusted in a fraction Serial No. 315,690.

of a second to the right current density and 'v my invention is characterized will herein- 'f after be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, referenee may be had to the following detailed description taken in connection with the accompanying drawings, wherein:

Figure l is a front view of a rheostat arranged in accordance with my invention, only a fragment of the base being shown; Fig. 2 is a rear view; Fig. 3 is a section on an enlarged scale taken Aapproximately on line 3 3 of Fig. l; Figs. 4 and 5 are fragmentary sections showing modiiications; Fig. 6 is a section taken approximately on line 6 6 of Fig. 5; Fig. 7 is a front or top view of a modified form of main arm for the rheostat; Fig. 8 is a section taken approximately on line 8 8 of Fig. 7 Figs. 9 and l() are sections taken respectively on lines 9 9 and l0 10 of Fig. 7; Fig. 1l is a detail of a modified form of the auxiliary section of the rheostat; and Fig. 12 is a front or top view of the rheostat arm shown in Fig. 11.

Referring to Figs. 1 to 3 of the drawings, l represent-sr a base in the form of a slab of insulating material. Mounted on the front or top of the base are a series of stationary segments 2, 2 arranged in an are of a circle and spaced apart from each other. Each. segment may have on the rear side a post Il extending through the base and constituting a terminal. The segments may be fastened to the slab by means of screws 4 extending into the same through the base. The segments constitute almost a complete circle, there being left a gap of about the size of one of the segments. In the circular space surrounded by the segments is a metal ring 5 having a wing 6; the wing 6 extending into the gaL between the two endlnost seginents and completing the circle. The wing G is provided with a post 'l' similar to the posts projecting rearwardly through the base. Un the rear side ot the base a second series ot segments 8, 3 ar 'aw'ed in a circle and spaced apart troni e..ch other. These segments are pre'ierab y mounted on lo a sniall ringlilie slab ot insulating material 9 lying against the rear tace or the base and secured to t1 suitable inanner.

nietal side ot the ot the ring a il base and s t screws l2. On tl the inain rheost lne latter ri a inountel end resting on end on the ring.

long e d ot the rheostat arni is a linob or handle 16 for turning` the saine. This end the arin is proyided on inner or underby a suitable plug lie). Upon remove plug, oil inay be introduced through i :t inT the oil groove to lubricate the which the lon end. ot the rheo- J t. There nia-,f be a similar oil d is desirable to have the rheod arni tend to coine to rest and be. yieldingly held in place whenever it is directly over one ot the segments. To this end I have provided a pawl and ratchet device consisting of a series ot recesses or depressions 2l di ributed about the ring 5 and g-pr sed plunger Q2 in the short end heostat arin. e sefinents Qv and the wing G may be proi'ide at )eriphery with an outwardly-dn'ecte 23 haring a flange 2l; oil'erot the rheostatarin as tter troni being litted oll the segments.

Cooperating with the segments 8 on the rear side ol the base is a s inging Contact In the arrangement shown7 this Contact is carried on the outer end ot a spring` arm 2G fixed to the rear end or" a shaft 2T that vided on their inner edges with hemispherical recesses 29 adapted to cooperate with .a spring-pressed plunger 30 extending radially iroin the shaft 27.

s best shown in Fig. 2, the posts 3 are connected in any usual or suitable way by nieans ot resistance elements whereas the contact segments S are connected by suitable resistance elements One line 3l is connected to a post 3 at one end e .e series while the other line wire is connected to the post T. The line wire 3l also connected to one of the segments S through a resistance 3G. It will thus be seen that a large Yvariation in the resistance be produced by turning the niain arm rheostat and, after it has been brought to rest on any of the inain contact segments, a liner regulation inay be ell'eeted by turn.- ing the auxiliary arin. The total number ot adjustments that may be inade thereaproxilnately equal to the nuinber of .pre niain segments multiplied by the nuinber ot the auxiliary seginents. As a result, the current values inay be varied by extremely small steps.

In Fig. l the rheostat arin 1B has an L-sliaped foot l0 itting int-o an arc-shaped groove l of similar' shape in the contact segment 2a.

In Figs. and G, the rheostat ar1n 'lf-l" has a lug projecting down into a wide arc-shaped groove l2-3 in the segment 2b. In the groove, eside the lug, is a shoe it between which and the lug are arranged springs 45, to insure good contact between the arin and the segment.

In Figs. 7 to l() I have illustrated a modified torni of inain rheostat arni. The arm, lil-C', has in one end a square or rectangular hole 5() extending through the saine. In this hole is slidably mounted a contact brush in the forni of a block 5l composed of copper gauze7 brass gauze, copper-carbon mi);- ture, solid brass or copper, or other suitable conducting material. On top ot the arm, at some distance above the block, is a stationary cross-piece Between the cross-piece and the contact block are springs A pigtail 54 has one end secured to the block, while its other end is secured to the arm. In the opposite end of the arln are two holes 55, 55. Slidably mounted in these holes are brushes or Contacts in the forni of blocks 56, :56, similar to the block 5l. A enrred leat spring 57 is secured at the iniddle to the arin at a point between the two brushes by ineans ot a screw 58 or the like; the ends of the spring pressing down on the blocks. The brushes are connected to the asin by suitable pigtails 59.

In Figs. 1l and l2 there is illustrated a niodilied 'forni oit auxiliary contact arni. On the shait Q7 is a. sleeve G0 from which projects a radial arin 6l whose outer end is in the form of an open frame 62. In the opening in the frame is a slidable contact block or brush 63. Secured at one end to the end of the shaft, by a screw G4 or otherwise, is a spring finger 65 Whose free end presses on the block to hold it in contact with the segments 8. A pigtail 66 extends from the brush to the shaft, the screw 64 serving the double purpose of securing the spring linger and the pigtail to the shaft.

It will thus be seen that I have produced a simple and novel rheostat by means of which line adjustment of the resistance can be made over a wide range by means that permit the use of a comparatively small number of resistance elements to produce a much larger number of adjustments. It will also be seen that the movable arms of the rheostat become yieldingly locked when they are brought to rest properly positioned over the cooperating stationary contacts. Also, in all forms of my invention, the movable Contact elements are yieldingly pressed into engagement with the stationary elements and the cooperating surfaces between the contacts are effectively lubricated so that the rheostat may at all timesbe easily operated.

I claim 1. In a rheostat, a base of insulating material, a rotatable shaft extending through said base, a series of main stationary contacts arranged in an are about said shaft on one side of the base, a series of auxiliary stationary contacts arranged in an arc about said shaft on the other side of the base, a contact mounted on said shaft in position to ride over the auxiliary contacts when the shaft is rotated, and a main contact arm mounted to rotate about said. shaft, the main arm engaging With said main stationary contacts.

2. In a rheostat, a base of insulating material, a post fixed to and projecting from the base, two sets of stationary contact elements mounted on opposite sides of the base in arcs of circles having their centers at the axis of the post, a main contact arm rotatable on the post and cooperating With one set of stationary contact elements, a shaft extending through the post and rotatable therein, a` contact arm on one end of the post cooperating With the second set of stationary contact elements, and an operating handle on the opposite endvof the shaft.

3. In a rheostat, a base of insulating inatcrial, a metal ring overlying and secured upon the base, a radial Wing projecting from the periphery of the ring, a series of stationary contact elements spaced apart from each other and from said Wing and forming with the latter an articulated ring spaced apart from the aforesaid ring, a rotatable contact arm extending radially of said rings and engaging with the latter,

there being recesses in the top of the central ring, and a spring-pressed dog on said arm in position to engage With one after another of said recesses as the arm is rotated, a terminal on said wing, a second terminal, and resistance elements connecting said second terminal with said stationary contact elements.

4c. In a rheostat, stationary contacts, a movable contact mounted to slide over the stationary contacts and in engagement therewith, said movable contact having in its Working'face a groove for receiving a lubricant, and there being a passage leading from said groove to the opposite face of the Inovable Contact to receive 'lubricating material and deliver it to said groove.

In testimony whereof, I sign this specification.

JULIUS BECKER. 

